(1) Field of the Invention
The invention relates to an arrangement for producing an air partition on a passage between rooms with different air temperatures. The invention may be applied to passages leading to objects for which the temperature of the air has to be maintained at a constant level, for example in warehouse facilities for storing perishable foods, chemicals, or other substances and materials requiring a constant temperature. The invention may also be applied to cooling chambers or refrigerating rooms.
(2) Prior Art
A variety of systems exist for producing air veils (or screens), air curtains or air partitions. These variations include those intended for screening off passages between rooms with greatly varying temperature levels. Partitioning passages leading to refrigerating rooms present a special problem. Relatively strong currents of compensation air are produced due to the great difference in the density of air having a warm or normal temperature level outside the refrigerating room, and the cold air prevailing within the refrigerating room. Also, the water vapor contained in the warmer air condenses on the interface between the different layers of air, producing an ice fog. The ice fog leads to icing phenomena in the passage. The icing occurs particularly in the area of impact of the air veils, as well as along the camber of the passage since the compensating flow and the load of moisture is the strongest in that area.
U.S. Pat. No. 2,775,187 describes an air flow barrier that prevents compensating air currents in an opening between two rooms at different temperature levels. The air flow barrier comprises a pair of air ducts of the same size that are arranged above the delimitation of the opening and within a cooling chamber. The air ducts are extended on flow chambers arranged on the jamb of the opening. These flow chambers have a curved front wall, a fixed plane back wall, a rib connecting the back wall and the front wall for separating the currents of air coming from the air ducts, and air-blowing nozzles located in the front wall. The nozzles are aligned in the longitudinal direction of the flow chambers and are set at a defined angle in relation to each other. The air ducts are connected with ventilators aspirating air from the respective room. A pair of air veils is produced in this way, flowing slightly away from each other and across the opening. The temperature of the air veils corresponds with the given temperature of the room air that is aspirated for producing the air veils. A drawback of this known solution is that the formation of ice fog is not prevented.
An air screen according to DE-PS 971 345 for room passages represents an advanced solution for preventing external air from flowing in through a passage due to difference between the temperature of the external air and the room air. This patent has air jets exiting from an air-blowing slot on one side of the passage and the room wall with an angle that is continuously changing or step by step over the clear height of the opening. The differences in the rate of inward flow prevailing on the opening in accordance with the height are taken into account in this manner.
The air xe2x80x9cdoorxe2x80x9d known from DE-PS 10 95 497 for dryers and industrial furnaces uses blowing slot areas whose angles can be adjusted, so that the blowing directions and ejection distances (or ranges) of the air jets respond to changing conditions by rotating individual or several nozzle sections against each other around their longitudinal axes.
However, neither of these references are intended or suited for screening off a passage leading to a refrigeration room. This problem is addressed by an air veil arrangement which, according to a company prospectus of the firm F. H. Biddle B. V. Kootstertille (Netherlands), is referred to as a xe2x80x9cMAT-Frigoschleierxe2x80x9d, and known also from EP 06 45 588. According to these documents, the passage is swept by a veil of air that consists of at least three partial air currents flowing in the vertical direction for the purpose of separating the room air of a deep freezing chamber from external air. The partial air outer currents are formed by the respective room air; the one or more center currents of air are taken from the dry room air of the deep-freezing chamber and heated before they flow out. This prevents condensation of water vapor contained in the warm external air on the interface with the dry cold air.
Ice fog is produced in connection with this solution, and the formation of ice fog and icing cannot be avoided in the areas that are farthest removed from the blowing nozzles, and in the area of the floor. This is caused by induction effects leading to mixing between the partial air currents, and between the partial air currents and the room air adjacent to the latter, as well as to the eddying of the partial air currents in the area of impingement. This eddying may cause portions of the relatively moist partial flow of warm air, which is loaded with moisture, to penetrate the refrigeration room. However, the load of water vapor is condensed there, resulting in icing.
These effects are amplified by the difference between the density of the cold air of the refrigeration room and the warm external air, and by the tendency to pressure compensation based on the difference in the density. The horizontal arrangement of the blowing nozzles above the passage and the formation of at least three partial air currents require relatively high expenditure for generating the required flow volume and the required flow rate so as to safely sweep the entire passage and prevent compensation currents.
Preventing induction from occurring between the partial currents of air is known from DE 199 32 708 A1. The arrangement produces a veil of air in a passage leading to a low-temperature chamber by supplying an air-blowing nozzle both inside and outside of the low-temperature chamber that is supplied with dry and heated air exclusively aspirated from the low-temperature chamber. The blowing directions are adjusted so that a crossing of the air currents takes place. In particular, the center blowing direction of the blowing nozzle arranged in the low-temperature chamber intersects the plane of the door. However, icing can be avoided only if the partitioning of the low-temperature chamber against compensation currents is cut back.
A combination of the known solutions fails to lead to a satisfying result. Accordingly, in spite of a multi-faceted search over many years, it has not been possible to resolve the screening off of rooms with air at different temperature levels because of the problem posed by ice fog formation and icing phenomena.
The present invention provides for the separation of air in a passage between rooms with different air temperatures while avoiding icing phenomena in conjunction with a significant reduction of compensation currents as well as expenditures.
The air intake (or suction) part of a first ventilator is arranged in a cooler room. The pressure side of this first ventilator is connected to a heating device that has at least one heating element and a device for controlling the loading temperature. The device is connected to a sensor arranged in a warmer room for detecting the partial pressure of the water vapor. The output of the heating device is connected to at least one first blowing nozzle, which is arranged in the cooler room vertically next to the passage. It is provided with a slot outlet extending over the entire height of the passage. A pair of first blowing nozzles are arranged in the cooler room on each of the two sides of the passage. These air-blowing nozzles are connected with the outlet of the heating device.
A second ventilator with an air intake part is located in the warmer room. A pair of second air-blowing nozzles is connected to the pressure side of this air intake part. These second air nozzles are arranged in the warmer room vertically on both sides of the passage, and provided with slot outlets extending over the entire height of the passage.
The slot outlets of the first and second air nozzles are divided in two sections that are displaced (or offset) in relation to one another. In the lower area the first blowing nozzles are set so that they are pointing away from the plane of the passage and offset by between 25xc2x0 and 45xc2x0. In the upper area the first blowing nozzles are adjusted so that they point in the direction of the plane of the passage, offset by between 15xc2x0 and 35xc2x0. The direction in which the second air-blowing nozzles are blowing out air, on the other hand, are set in the lower area offset by between 5xc2x0 and 30xc2x0, pointing in the direction of the plane of the passage, and in the upper area offset by between 25xc2x0 and 45xc2x0, pointing away from the plane of the passage.
The size of the cross sectional areas of the first and the second air-blowing nozzles, and the width of the gaps of the slot outlets of the first and the second air-blowing nozzles are coordinated depending on the width of the passage and the temperature difference between the cooler room and the warmer room.
The heating element is operated above a 2 mbar limit value of the water vapor partial pressure of the air of the warmer room depending on the water vapor partial pressure of the air of the warmer room, width of the passage opening, and the temperature difference between the air in the cooler room and the air in the warmer room. Both the warmer and the cooler areas may be located in the same building. Likewise it is possible that either the cooler or the warmer area is located in a building, and the other area externally adjacent to the building.
The invention produces a partial current of air that is dry to the highest possible degree. It has a temperature that is controlled by the water vapor partial pressure of the air in the warmer space, which raises the capacity of the dry partial current of air to absorb moisture and thus prevent saturation that leads to the formation of ice fog on the interfaces of the partial currents of air producing the partition. Any icing is prevented in this manner within the area of the passage. The partial currents of air can be produced in an effective manner in terms of energy. Due to the development of a vertically resulting line of back-up in the center of the passage from the flat and directed jets of air acting over the entire height of the passage, both the discharge of cold air flowing from the cooler space, and the current of warm air flowing into the cooler space, accepting cutbacks within the partition is completely prevented.
The jet pulse of the first air-blowing nozzles may be twice as high as the jet pulse of the second air-blowing nozzles. Depending on the temperature difference and thus the difference in the density between the air of the cooler space and the air in the warmer space, the slot outlets are optimally divided in upper and lower areas. The divisions start from a center division based on the total length of the slot outlets. They permit the development of the optimal back-up line depending on the typical compensation tendencies of the air flow. The same purpose is served by the way the plate impinged upon is arranged above the second air-blowing nozzles, in that induction between the exiting partial flow of warm air and the air present above the second air-blowing nozzles is prevented from occurring within the proximity of the passage. This is also achieved by the formation of a gate, which is an extension of the jamb of the passage into the warmer space. Uncontrolled currents are excluded by arranging the first air-blowing nozzles on the wall of the cooler room or space with no gaps in between, to the greatest extent this is possible.
The development of an optimal line of back-up is made possible even under variable conditions by rotating the air-blowing nozzles and/or by turning the sections of the air-blowing nozzles. This rotation may take place manually or in an automated manner, whereby in addition to the temperature difference between the air of the cooler space and the air of the warmer space, it is possible to detect and factor in the wind load if the passage leading into the external area is involved.
The gap widths of the second air-blowing nozzles are dimensional so that the gap widths of the lower slot outlet areas amount to from 60% to 80% of the gap widths of the upper slot outlet areas. Any superimposition of the lower streams of air being blown out by the first and second air-blowing nozzles is avoided. Any penetration of warm air into the cooler room by the lower stream of air blown out by the second air-blowing nozzles that may occur, is thus prevented. By arranging the air intake part of the first ventilator remotely from the passage, it is assured that the current of partitioning air in the cooler room or space is loaded with moisture only to the lowest possible extent. The design of the heating element in the form of a heat-storing heater system reduces the energy requirements and enhances the control property of the heating device so that thermal energy can be continually xe2x80x9ccalled inxe2x80x9d for heating the air aspirated from the cooler room.
The application of the invention is not limited to partitioning off rooms (or spaces) with different air temperature levels. By modifying the components of the arrangement and/or the overall arrangement as defined by the invention, with respect to its components, it is possible to realize both general and otherwise application-specific air partitioning or air veil solutions in accordance with the invention. This applies to, for example, air partitioning arrangements for operating systems, manufacturing plants and other industrial and service areas, as well as to luggage conveyor systems installed, for example at airports or railway stations.